The majority of inks and toners used in the printing industry employ water insoluble polymers for print adhesion and durability. Water-based inks, such as used in ink-jet printing, can incorporate water insoluble polymers as dispersed particulates. The particulates are typically designed to allow formation of a print-film on the printed substrate. Alternatively, these water insoluble polymers can be coated on the surface of pigments in the form of polymer-encapsulated pigments.
While some encapsulation methods and chemistries are known, dispersions including such polymer encapsulated pigments often don't exhibit stability in dispersions having relatively high solids content. Therefore, many encapsulation methods, e.g. those including potassium persulfate, are carried out with low solids content. Unfortunately, although dispersions with lower solids content exhibit improved stability, they are difficult, if not impossible, to utilize in such products as inks. As dispersions having low solids content, and thus low pigment content, are diluted by incorporation into an ink, the overall pigment content of the ink is likewise limited.
Thus, there is a continued need for development of stable polymer encapsulated pigment dispersions that have high solids content.